Fusing photons into diphoton resonances at Belle II and beyond

TL;DR

This paper proposes a new method to search for diphoton resonances at Belle II, demonstrating improved sensitivity over previous channels and highlighting the benefits of extending detector coverage for future discoveries.

Contribution

It introduces a novel search channel for diphoton resonances at Belle II and analyzes how detector coverage extensions can enhance detection prospects.

Findings

The new $e^+e^-+ ext{diphoton}$ channel offers better reach than the $ ext{photon}+ ext{photon} ext{photon}$ channel in most mass ranges.

Extending Belle II's forward coverage significantly improves sensitivity, even with reduced luminosity.

Forward extension can outperform increased luminosity in certain scenarios.

Abstract

We propose a new search for a diphoton resonance in the $e^+e^-+\gamma\gamma$ final state at Belle II that improves the expected reach compared to the $\gamma+\gamma\gamma$ channel in most of the available mass range. For simplicity we show our results in the simple parameter space of an ALP coupled solely to Standard Model photons. In addition, we show how an extension of the forward coverage of Belle II, or another similar experiment at the high intensity frontier, could improve the reach in our channel. We show that such a forward extension can be advantageous even with a loss of a factor 100 in luminosity compared to Belle II.